Networked devices typically comprise at least two components: a network interface controller (NIC) and a central processing unit (CPU, or “host”). The networked device may be connected to other networked devices via a network, such as a local area network (LAN), a metropolitan area network (MAN), or wide area network (WAN) such as the Internet. Networks may utilize wired networking technologies and/or wireless networking technologies. IEEE 802 describes communication architectures, which enable networked devices to communicate via a LAN or MAN.
A given networked device may utilize procedures to reduce power consumption. When reducing power consumption the host may enter an inactive state while still enabling the networked device to be accessible to other networked devices on the network. In wired networks, a common method used by networked devices for reducing power consumption is known as “Wake on LAN” (WoL).
In WoL systems, the host may program the NIC to monitor traffic received from the network based on a filter or set of filters. The filter(s) may be utilized by the NIC to perform pattern matching operations on packets received from the network. The host may then enter a low power, or inactive, state. While the host is in the inactive state, the NIC may continuously monitor traffic received from the network. When the pattern matching operations indicate receipt of a packet that matches one of the filters, the NIC may send a wakeup signal to the host, causing the host to exit the inactive state and to subsequently enter an active state. The transition from inactive state to active state may correspond to increased power consumption at the networked device.
IEEE 802.11 describes a communication architecture, which may enable networked devices to communicate via wireless local area networks (WLANs). One of the building blocks for the WLAN is the basic service set (BSS). A BSS may comprise a plurality of networked devices, or stations (STA), which may communicate wirelessly via one or more RF channels within a coverage area. The span of a coverage area may be determined based on the distance over which a source STA may transmit data via an RF channel, which may be received by a destination STA.
An independent BSS (IBSS) refers to a BSS, which comprises a set of STAs, which may communicate with each other over within the coverage area for the BSS. In an IBSS each STA may engage in direct communication with any of the other STAs within the IBSS. An IBSS may be referred to as an ad hoc network.
An infrastructure BSS refers to a BSS, which is one of a plurality of BSSes, which are associated in a larger network referred to as an extended service set (ESS). The ESS is identified by a service set identifier (SSID). An infrastructure BSS may also be referred to as a BSS. Each of the BSSs within an ESS is identified by a BSS identifier (BSSID). Thus, STAs within a BSS generally determine their association within the BSS based on a BSSID and an SSID.
Communication between BSSs occurs via a distribution system (DS). The DS may utilize wired and/or wireless communication technologies. A BSS is able to establish communication to the DS via an access point (AP). The AP is a member of the BSS.
Each BSS comprises a plurality of STAs and an AP. The AP forms an association with each of the STAs within the BSS. The AP identifies each association by an association identifier (AID). The AP may provide communication services to STAs within a BSS based on the presence of an established association.
Within an infrastructure BSS, communication between STAs typically occurs via the AP. For example, when a STA_A within the BSS attempts to communicate with a STA_B within the BSS, the STA_A sends data to an AP_1, which subsequently sends the data to the STA_B. When the STA_A within BSS_1 attempts to communicate with a STA_X within a BSS_2, the STA_A sends data to the AP_1 within BSS_1. The AP_1 sends the data via the DS to an AP_2 within the BSS_2. The AP_2 sends the data to the STA_X within the BSS_2.
Within a BSS or IBSS, a STA may operate in two power management modes: an active mode (AM) and/or a power-save mode (PS). When the STA is operating in the AM, the STA may be fully powered (within the capabilities of the power supply, for example) and may transmit and/or receive data. When the STA is operating in the PS mode (or “sleeping”), the STA may enter a doze state during which it operates at lower power consumption (when compared to AM) and capabilities for receiving data may be disabled. In an IBSS, a STA communicates its current power management mode to each of the other STAs within the IBSS. In a BSS, a STA communicates its current power management mode to the AP.
When a STA within a BSS is operating in an AM, the AP may send data to the STA. When the STA is operating in PS mode, the AP may store, or buffer, data, which is to be sent to the STA. At determined time intervals, the AP transmits beacon frames to the STAs within the BSS. STAs, which are operating in PS mode, may depart from the doze state during these time intervals to receive the beacon frames. The beacon frames may comprise a traffic indication map (TIM) information element. The TIM element comprises data, which indicates whether the AP is currently buffering data for one or more STAs within the BSS. Beacon frames may comprise a delivery TIM (DTIM) element. In the TIM element, a DTIM count enables the determination of whether the beacon frame contains a TIM or DTIM. When DTIM count equals 0, the TIM element is a DTIM element. In addition to the buffered unicast indication, a DTIM element comprises data which also allows the STAs to determine whether the AP is currently buffering data to be broadcast or multicast to a plurality of STAs within the BSS. The TIM (DTIM) element comprises a plurality of indication values, which are located based on an AID. For example, a STA may determine whether the AP is currently buffering unicast data by indexing the TIM data based on the AID assigned to the STA for its association with the AP. Additionally, a STA may determine whether the AP is currently buffering broadcast and multicast data by indexing the DTIM data based on the AID designated for the buffered broadcast and multicast traffic indication for the BSS.
When a STA determines that broadcast and multicast data is being buffered at the AP, the STA may leave the doze state to receive the buffered data. When a STA determines that unicast data is buffered at the AP, the STA may enter AM or poll the AP to receive the buffered data.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.